Despite the nearly universal employment of digitalis in the treatment of chronic congestive heart failure (CHF), there is no objective documentation of its long-term efficacy. The current project is designed to evaluate, in a double blind crossover fashion, the effects of maintenance digoxin therapy in chronic stable CHF, utilizing clinical findings, chest radiography, echocardiography and systolic time intervals to assess baseline left ventricular function non-invasively and maximal exercise testing to determine aerobic work capacity.